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Ada Programming

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Welcome to the Ada Programming tutorial at Wikibooks. This is the first Ada tutorial covering the Ada 2005 and 2012 standards. If you are a beginner you will learn the latest standard — if you are a seasoned Ada user you can see what's new.

Current Development Stage for Ada Programming is " (Feb 26, 2012)". At this date, there are more than 200 pages in this book, which makes Ada Programming one of the largest programming wikibooks.[1]

But still there is always room for improvement — do help us to expand Ada Programming. Even beginners will find areas to participate.

Ada puts unique emphasis on, and provides strong support for, good software engineering practices that scale well to very large software systems (millions of lines of code, and very large development teams). The following language features are particularly relevant in this respect:

An extremely strong, static and safe type system, which allows the programmer to construct powerful abstractions that reflect the real world, and allows the compiler to detect many logic faults before they become errors.

Modularity, whereby the compiler directly manages the construction of very large software systems from sources.

Information hiding; the language separates interfaces from implementation, and provides fine-grained control over visibility.

Readability, which helps programmers review and verify code. Ada favours the reader of the program over the writer, because a program is written once but read many times. For example, the syntax bans all ambiguous constructs, so there are no surprises, in accordance with the Tao of Programming's Law of Least Astonishment. (Some Ada programmers are reluctant to talk about source code which is often cryptic; they prefer program text which is close to English prose.)

Portability: the language definition allows compilers to differ only in a few controlled ways, and otherwise defines the semantics of programs very precisely; as a result, Ada source text is very portable across compilers and across target hardware platforms. Most often, the program can be recompiled without any changes.[2]

Standardisation: standards have been a goal and a prominent feature ever since the design of the language in the late 1970s. The first standard was published in 1980, just 3 years after design commenced. Ada compilers all support exactly the same language; the only dialect, SPARK, is merely an annotated subset and can be compiled with an Ada compiler.

Consequences of these qualities are superior reliability, reusability and maintainability. For example, compared to programs written in C, programs written in Ada 83 contain "70% fewer internal fixes and 90% fewer bugs", and cost half as much to develop in the first place[3] Ada shines even more in software maintenance, which often accounts for about 80% of the total cost of development. With support for object-oriented programming, Ada 95 may bring even more cost benefit, depending on how objects are used; although no serious study comparable to Zeigler's has been published.

In addition to its support for good software engineering practices, which are applicable to general-purpose programming, Ada has powerful specialised features supporting low-level programming for real-time, safety-critical and embedded systems. Such features include, among others, machine code insertions, address arithmetic, low-level access to memory, control over bitwise representation of data, bit manipulations, and a well-defined, statically provable concurrent computing model called the Ravenscar Profile.

Other features include restrictions (it is possible to restrict which language features are accepted in a program) and features that help review and certify the object code generated by the compiler.

Several vendors provide Ada compilers accompanied by minimal run-time kernels suitable for use in certified, life-critical applications. It is also possible to write Ada programs which require no run-time kernel at all.

It should come as no surprise that Ada is heavily used in the aerospace, defence, medical, railroad, and nuclear industries.

The Ada Reference Manual (RM) is the official language definition. If you have a problem and no one else can help, you should read the RM (albeit often a bit cryptic for non-language-lawyers). For this reason, all complete (not draft) pages in Ada Programming contain links into the appropriate pages in the RM.

The RM is a collective work under the control of Ada users. If you think you've found a problem in the RM, please report it to the Ada Conformity Assessment Authority. On this site, you can also see the list of "Ada Issues" raised by other people.

Unlike other programming languages, Ada compilers are officially tested, and only those which pass this test are accepted, for military and commercial work. This means that all Ada compilers behave (almost) the same, so you do not have to learn any dialects. But because the Ada standard allows the compiler writers to include some additions, you could learn a cool new feature only to find out that your favourite compiler does not support it...

The following are collection pages. All collection pages are comprised of groups of the already available pages. You can use them for printing or to gain a quick overview. Please note that those pages are partly very long.

The Source from the Book is available for download and online browsing. The latter allows "drill down", meaning that you can follow the links right down to the package bodies in the Ada runtime library.